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I have had my p85 for just over a week. I have charged several times with as little as 39 miles range left to more normal 150 before I charge. Pluged into my home 14-50 plug charging at 39 to 40 volts at about 235 watts I get 18 to 21 miles added per hour. Tesla on their web page states 31 per hour, and I know this is ideal conditions. But I only see 18 to 21. I am being told my charger is working fine and my rate charging per hour is based on my driving habits. Habits are how much I use climate control, radio, etc. I don't think that should make any difference on my recharge rate per hour, only total range needed to be charged . This concerns me if I need to charge on the road. If I need to add 60 miles it is the difference between 2 or 3 hours waiting for charge.

Can anyone tell my what you are adding using a 14-50 plug and in your experience does the use of your climate control, radio, seat heater make any difference in your rate of recharge per mile added?

clr4option | 14 Février 2013

The 31mi charging is based off ideal milage which will equate to somewhere in the 20s on rated. I suggest you go into your settings and select "energy" under charging units. The display will then reflect the 10kw charging rate you are and should be getting.

jat | 14 Février 2013

It seems a bit low -- I normally see 22-24 rated miles/hr. Your voltage is only 235, but that should be maybe 1mi/hr lower.

Mark Z | 14 Février 2013

The charging should start slow and rise to the correct level after a few minutes. I was told the charger in the vehicle does analyze the power received and adjusts accordingly. 21 mph appears to be closer to a 30 amp supply. I know it sounds strange, but if the wire size or length from the circuit breaker to the outlet is not rated for 50 amps, then less current may flow. Call Tesla for more advice and try another NEMA 14-50 location. Visit an RV park if necessary and request a 50 amp circuit.

DouglasR | 15 Février 2013

You probably mean you are charging at 39 to 40 amps and 235 volts, not 39 to 40 volts and 235 watts.

There are several factors that affect charge rate in addition to the reported voltage and amperage. As others have mentioned, when the battery charge approaches completion, charging slows down. Also, the car is often running various systems while it charges. Sometimes the heat goes on (especially if you are sitting in the car), and sometimes the air suspension compressors operate. This will draw current away from charging, and charging will slow.

Finally, I am not sure that the rate of charge is always reported accurately. I find that the number jumps around a lot. The real test is how fast does it add miles and reach completion?

Carmine | 15 Février 2013

My TS charges at that same 18-21mph range as well. My electrician tested the 14-50 immediately after installing
It and found the line to be at 100%. To this point I have only driven short distances before recharging and that may have something to do with it.

STARR X | 15 Février 2013

I had an outlet installed at work. The building has 3 phase coming into it. I used a 50 amp breaker. The electrician put a voltmeter up to the socket after installation and it registered 258 volts. He informed me that the power coming through the power line can vary by 10%. But this being said, the most mile per hour being charged I have seen is 29 miles. And I have also seen less (low 20's).

Hills | 15 Février 2013

This is also a topic that has been covered many times on the forum if you search.

I've had the car for 10 weeks, and I use NEMA 14-50. For me, the voltage always drops from 243V to about 234V when charging at 40 Amp. The rate of charge ranges from 22 to 26 miles per hour with 24 mph the most common. YOu should go back to the car 15 minutes after plug in to see steady state charge. Also do an experiment. I find that the actual charge is consistently faster than what the instrument panel says.

jjaeger | 15 Février 2013

My experience is similar to Hills. Nice thing now however with the Android & iOS apps out - can do a quick check remotely that the MPH has crept up to the usual steady state value after a few minutes. And I agree with Hills, in that while it reports a given MPH value, looking at the time remaining, if usually finishes right as scheduled with an effective rate over that time higher than what was displayed. Have not analyzed closely to understand the exact deltas, but am comfortable now that I can check with my phone when it said it would be complete, it is - and I go out an move my car (when at work) as we have more EVs than charging locations.

Brian H | 15 Février 2013

Seems like that low "rate" readout is something a S/W update should target and fix.

DTsea | 15 Février 2013

I seem to get about 28 mi per hour. Check how many amps you are drawing. 235V and 25 amps sounds like 21 mi/hr. you can draw up to 40 amps continuous on a nema 14-50.

Hills | 16 Février 2013

Conclusion: probably not much to worry about.

Just recorded more data. Started to charge my 85Kwh car with the car at 95 rated miles, this is lower starting point than normal for me. Voltage dropped from 242 to 230, and the drop is lower than normal. Amp is 40. After 5 minutes, the instrument panel says 22 miles/hour, and it would take 5 hours and 15 minutes to standard charge (the math does not make sense, but it has never made sense)

Exactly one hour later, I come back to the car. The car reads 124 miles, so 29 miles were added! Instrument panel states 26 miles/hour, obviously there is a software display problem. Amp is still 40, voltage is 233.

Yes, the instrument panel charge rate consistently understates actual charge rate. At exactly the 4 hour mark, the rated miles read 212, which means just over 29 miles charged per hour, while the screen still read 26 miles/hour, and Voltage still at 233. In spite of 233V, I got 29.25 rated miles/hour!

Superliner | 16 Février 2013

Perhaps the algorithm calculates charge rate over "total time" to completion and that rate is what you see on the display. Battery conditioning also occurs "or can" while charging which would reduce the effective rate of charge while warming / cooling the pack.

The "Ideal" conditions spoke of also say "assumes 250v circuit". It is unlikely any of us will routinely see "ideal" conditions under which to charge. It does not appear that you have anything to worry about.

Hills | 16 Février 2013

@superliner,
This is one of the few metrics that exceeds what Tesla claims! Many people on the forum have reported low charge rates. I have recorded the charge rate experiment many times. The actual "rated" miles charged repeatedly comes in higher than the charge rate, and both numbers are displayed on the same instrument panel at the same time. I believe the actual miles charged, not the charge rate. My realized charge rate equates to 36 ideal miles per hour!

Superliner | 16 Février 2013

@ Hills

That sounds like a good thing, I have to listen more than speak however as I have no practical experience with a Model S (don't have a car "yet"!)

Always nice to over perform (but one would think it should be accurate) There have been others (other threads) that state 21 - 24 mph on a 14-50 what am I missing ? Help?

Hills | 16 Février 2013

@Superliner,
I've had the car 10+ weeks now. Model S is a great car but there is no such thing as a perfect car. This car has its share of small issues. I used to puzzle of this charge rate issue but my conclusion is don't worry.

There are many people who wonder about the low charge rate. I think there are many explanations.
Some don't know the difference between ideal miles and rated miles.
Some don't have 40 A or 240V.
Some look at the charge rate after plugging in, not realizing that it takes some time for the charge rate to reach steady state, I'd say 10+ minutes.
Finally, the charge rate consistently understate reality, as I repeatedly proved. I believe others will come to my conclusion. Today, I was surprised that the realized charge rate did not slow down much even as it approached 240 rated miles.

Superliner | 16 Février 2013

Thanks Hills.

Brian H | 16 Février 2013

Yes, it seems the "slowing" mainly affects the SuperCharger. It falls back to the lowly HPWC level!

bobinfla | 17 Février 2013

This had me concerned at first, but after watching it for a while, it seems that it gives a low mph number but knows what it's really charging at because it correctly calculates the time to complete charging based on that.

For example, if you're at 100 miles and plug it in, it says it is charging at 23 mph and will be done in 5 hours, and then it really is done in 5 hours with a range showing of 240 miles. That means it put 140 miles range on in 5 hours = 28 mph, not the 23 it was saying.

jackhub | 17 Février 2013

I'm using a 14-50 and I show 27-29 amps during charging. vin 3059, 85Kwh.

jackhub | 17 Février 2013

I should have added that when charging begins it is in the neighborhood of 10 amps and then slowly builds up to 27-29 amps in about 5-10 minutes. I don't know why there is a slow build up. vin 3059, 85Kwh.